Rotary finder and secondary



Sept. 4, 1956 C. E. LOMAX ROTARY FINDER AND SECONDARY Filed March 10. 1953 LINE CKT lOI 5 Sheets-Sheet 1 FINDER I02 I M "E INVENTOR. CLARENCE E. LOMAX ATTY.

' Sept. 4, 1956 c. E. LOMAX 2,761,906

ROTARY FINDER AND SECONDARY CLAREN CE E. LOMAX ATTY.

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ATTY.

United States Patent ROTARY FINDER AND SECONDARY Clarence E. Lomax, Chicago, 111., assignor to Automatic Electric Laboratories, Inc., Chicago, 11]., a corporation of Delaware Application March 10, 1953, Serial No. 341,490

11 Claims. (Cl. 179-18) This invention relates in general to telephone systems and more particularly to switching systems therein.

One of the earlier switches used in telephony, the plunger line switch, had the advantage of being associated with a particular subscriber line and was always standing opposite an idle trunk, thereby reducing to a minimum the time required to connect the calling line to a first numerical switch. However the necessity for economy resulted in replacement of the line switch with a finder switch common to a group of lines, but the finders have had the disadvantage of a short time delay before connecting a calling line to a first numerical switch. The delay time was shortened somewhat by the use of double wipers hunting simultaneously over pairs of lines; but this resulted in the use of additional relays to prevent the finder from switching through to both of two calling lines, the time delay being dependent partly upon the operating time of said additional relays.

Applicant has now eliminated the necessity for said additional relays to achieve economy; and, by making use of a new and novel means by which both theswitching relays and the magnet respond directly to potential conditions on test contacts, applicant has further reduced the time delay. 7

It has been known that the use of an inexpensive secondary switch could achieve economy by reducing the number of expensive first numerical switches necessary for a predetermined grade of service. However, in the past the appreciable increase in the time delay before connection of the calling line to a numerical switch made such a scheme commercially impracticable.

t is urged that applicant has solved the latter problem by using, in conjunction with his new and improved finder, a secondary switch with double wipers which hunt simultaneously over two trunks while the finder hunts for a calling line. Thus the time delay factor is not noticeably changed, especially since usually there will be fewer trunks over which the secondary switch must hunt. Also applicant has incorporated in the secondary switch a new and novel means, similar to that used in the finder switch, by which both the switching relays and the magnet are responsive directly to potential conditions on the test contacts associated with said trunks, thereby to reduce the time delay factor.

By use of absence of ground searching in both the finder and the secondary switch, applicant provides for the use of high speed rotary switches with a positive meansfor stopping the wipers on the desired line or trunk. As a result the time delay factor is further reduced, and a new, economical, highly flexible findersecondary switching system is now commercially feasible.

A preselecting finder-allotter 311i) is utilized to further reduce the time delay factor.

An object of this invention is a reduction in the number of expensive numerical switches necessary to provide a predetermined grade of service.

It is an object of this invention to provide a new and 7 all allotters. The first impulse received over conductor 2,761,906 Patented Sept. 4, 1956 ice novel switching system having means for more rapidly searching for and switching through to a desired line.

A feature of this invention is the use of a new and novel finder-secondary switch link.

A feature of this invention is the use of a new and novel switch of the type having a non-numerical or partially non-numerical function.

Another feature is the use of a new and novel shuntfield driving magnet in a non-numerical or partially nonnumerical switch.

Another feature .is the use of new and novel circuits with a shunt-field driving magnet.

Another feature is the new and novel means for preventing the release of the cutofi relay of a busy line circuit until after the restoration of the switching relay of the finder to which said line circuit has been connected.

Further features of this invention will become evident upon a perusal of the following disclosure in which:

Fig. 1 shows a substation, the line of circuit associated therewith and a finder having access thereto;

Fig. 2 shows a secondary switch associated with the finder shown in Fig. 1; and

Fig. 3 shows an allotter to which said finder and said secondary switch are available.

In the arrangement shown in the attached drawings,-

a shunt-field motor magnet with two windings and a single armature has been used for the first time in switches. A shunt-field relay has been previously .used in conjunction with a driving magnete. g. the Martin Patent No. 1,564,487-but this resulted in a more expensive switch and in a slower operation of the switch.

The present circuits have been arranged such that a magnet winding will be operated and the switching relay, associated therewith, short circuited if the test wiper associated with said winding :and relay encounters ground. If said wiper encounters absence of ground, said relay will operate in series with said winding; but the winding will not operate. If both test wipers encounter absence of ground at the same time, that switching relay, which operates first, will open the operating circuit to the other relay to prevent its operation.

The shunt-field magnet will operate its armature to step the wipers only if .both windings thereof are energized-as described in the Erickson Patent No. 1,544,300.

It will be noted that the use of the shunt-field magnet need not .be restricted to finders and secondary switches; rather it may be used in any non-numerical or partly non-numerical switch, such as an allotter or a selector, with. variations in the circuits disclosed herein.

Off-normal springs 297, 298 and 299 are provided in the secondary switch to busy mark the link while it is in use and to cause the switch to return to home position when it is released. In this manner, the numerical switches accessible to the switch are taken .into use in a definite order of priority. It may be of advantage, then, to make some of the selectorsthose to be taken into use lastavailab'le from more than one group of lines, thereby to furtherreduce the number of "selectors necessary in a system and increase the flexibility therein.

A means, well known in the art, for kicking the allotter oii :a defective finder-secondary switch link is provided. When R330 operates in response to a call, it prepares at contacts 334 a circuit for operating kick-cit relay R350. Timed impulses. are received over conductors 398 and 39.9 from a timing device (not shown) common to 399 after contacts 334' operate will operate R350. The next impulse received over conductor 398 and operated contacts 351 will operate M310 to step the allotter wipers to the next accessible link. This last impulse will short circuit R330; R330 will restore to open contacts 334;

R350 will restore; and R330 will reoperate when contacts 311 restore.

Any one of several selectors well known in the art may be used with the switches disclosed hereine. g. that shall be used with respect to the description ofthe operationof the switches shown herein.

' A more detailed description of the operation of the system will now be made. When a subscriber lifts the receiver at substation 100 a circuit, including said sub- R120 removes ground from testcontact 165 and places thereon battery from cutoff relay R110; at contacts 123, busy marks the line to all connectors having access thereto; and at contacts 125, completes a circuit, including start lead 171, relay R330, the winding of the allotter motor magnet M310 and 'its self-interrupting contacts 311, for operating the allotter startrelay R330. M310, however, does not operate. Assume allotter 300 has preselected idle finder 102 and idle secondary switch 200. At contacts 333, R330 completes an obvious circuit for operating hold relay R340; at contacts 335, grounds the all trunks busy conductor 173, thereby to maintain all trunks busy relay R320 operated-even though all other finders are in use-until finder 102 and secondary switch 200 complete their operations; and at contacts 336, ,completes a circuit over conductor 281 for operating the start relay R210 of the finder-secondary link. Hold relay R340 operates and at contacts 343 and 344 places an alternate ground on conductors 173 and 281.

Link start relay R210 operates; contacts 215 and 216 operate faster than contacts 213 and 214 to assure the short circuiting of the switching relays R130 and R140 prior to the completion of their operating circuits if the lines, upon which the finder wipers are standing, are noncalling lines so that the finder cannot falsely switch through to a non-calling line; and contacts 224 and 225 operate faster than contacts 211 and 212 to similarly prevent the secondary switch from falsely switching through to a busy numerical switch.

R210 completes a circuit over contacts 212, relay R250, contacts 235, 220 and 271 and magnet M270 for operating the secondary switching relay R250, a similar circuit for operating the secondary switching relay R230;

shown in the NewstedtPatent No. 2,529,409, which selector station and the 'line'associa'ted therewith, for operating. line'relay R120is completed. At contacts 121 and 122,

a circuit over contacts 213, conductor. 179, R130, and

contacts 146 and 152 for operating the finder switching relay R130, a similar circuit for operating the finder switching relayR140, and a circuit over contacts 218 and hold conductor 174 to maintain the allotte r start relay operated until the secondary switch switches through connections to an idle trunk, if the finder switches through to the calling line to remove ground from start lead 171 before the secondary switch completes its operation.

If the finder wipers are standing on lines other than the calling line and that line paired therewith, the test wipers 166 and 168 will encounter ground on'thetest contacts. ground over contacts 114 and 122 is placed on test contact 165. When a call has been initiated over line circuit 101 and extended by finder 102, ground is placed on contact 165 over contacts 134 and wiper 166. If a call has been extended to line circuit 101 over a connector, then ground is placed on contact 165 over private conductor 103 and contacts 124 and 113.) Ground over wiper 166, conductor 182, contacts 216, conductor 183 and contacts 136 and 146 will short circuit R130 before it can operate and will energize the upper winding of finder 'motor magnet M150; similarly ground over'wiper 168' will short circuit R140 and energize the lower winding of M150. When both of said windings are energized the armature of M150 operates, self-interrupting contacts 151 and 152 operate to open the energizing circuits of both windings, the windings will deenergize, and the finder (Note that, when line circuit 101 is idle,.

: its operation.

wipers will be advanced one step. If the wipers do not encounter the calling line circuit 101, M150 will again be operated similarly to again advance the wipers. This will continue until the finder'wipers encounter line circuit 101.

If, when start relay R210 operated, the finder wipers 162, 164 and 166 had been standing on contacts 161, 163 and 165 or if, thereafter, said wipers are advanced to said contacts, ground will not be found on test contact 165; as, a result thereofithe upper winding of M150 will not be energized sufliciently to cause an operation of the magnet armature; and switchin' relay-R130 will I operate in series with the upper winding of M1 50, At contacts 131 and 132, R130 extends-the-calling line over conductors 176 and 177 to the secondary switch; at contacts 133 prepares a circuit for holding itself operated after the restoration of start relay R210; at contacts 134, completes a circuit over wiper 166 and contacts 121 for operating the cutoff relay R110; at contacts 135, opens the circuit for operating switching relay R140; at contacts 136, opens its original circuit ,to wiper 166, thereby to revent the winding of R130 from being short-circuited after it has operated; at contacts 138, prepares a circuit over guard conductor 172 for busy marking the findersecondary link, and at contacts 139, removes one ground from the all trunks busy conductor-173. Similarly, if a calling line is encountered by wipers 168, 169 and 170,

switching relay R140instead of R130 will operate and at its contacts 141 and 142 extend said last-mentioned calling line to secondary switch 200.

If said wipers encounter two calling lines simultaneously, whichever switching relay operates first will open the circuit for operating the other, thereby to prevent (It will be noted that the cutoff relays e. g. R110have high resistance windings so that a switching relay connected thereto-e. g. R130 over contacts 136,

conductor 183, contact 216, conductor 182 and contacts 121-will not operate.) If it should happen that both switching relays operate simultaneously'each of said relays will open the operating circuit of the other; and both will begin to de-energize. In practice, it has been found that one will restore its contacts before the other even though they are similarin design. Whichever contactse. g. 135 or 146restore'first, those contacts will again complete the operating circuit of the other relay to maintain it operated. Therefore, it is evident that only one of said switching relays will switch through connections from a calling line to secondary switch 200.

When cutoif relay R operates in response to'the operation of switching relay R130, it opens contacts 111 and 112 to restore the line relay R and locks itself operated over contacts 113 to prevent its restoration when R120 restores to open contacts 121. R120 restores to remove its ground at contacts from the allotter start lead 171. The line is busy marked in the connector banks by ground over contacts 134, wiper 166, contacts 113 and restored contacts 124. If finder 102 switches through to the calling line before secondary switch 200 finds and switches through to an idle selector, and if no other call has been initiated in the meantime, ground will have been removed from start conductor 171; but start relay R330 willbe maintained operated over a' circuit including contacts 218, 238 and 258 and hold conductor 174. This circuit will be opened.

As previously described, circuits for operating the switching relays R230 'and R250 of secondary switch 200 are completed in response to the operation of start relay R210. The private contacts of the selectors accessible,

to secondary switch 200-e. g. contacts 293 and 295 will be marked with a ground potential if busy and'an absence of ground condition if idle. Secondary switch 200 will hunt for an idle selector and switch through connections to only one idle selector in a manner similar to that in which finder 102 hunts for and switches through to one calling line as previously described.

Therefore, only if ground potential is encountered by wipers 294 and 296 on both of the pair of contacts they seize, will both windings of motor magnet M270 energize to advance the wipers one step-the upper winding of M270 being energized over a circuit extending from the grounded wiper 294 over contacts 224, 255, 235 and 220 to said upper winding and the lower winding of M270 being energized over a circuit extending from the grounded wiper 296 over contacts 225, 236, 256 and 222 to said lower winding.

When an absence of ground condition is encountered by one or both of said secondary switch wiperse. g. 296-the winding associated therewith will not be fully energized, the magnet will not operate, and the switching relay-e. g. R230associated therewith will operate to switch through connections to the selector associated with said absence of ground condition.

Assuming that a call is initiated from substation 100, that finder 102 by means of R230 extends the line associated therewith to secondary switch 2'00 by way of conductors 176 and 177 and that switching relay R230 switches through connections to the selector associated with private contact 295, the line associated with substation 100 will be extended to the line relay of said selector by way of contacts 131 and 132, conductors 176 and 177, and 281 and 232, contacts 231 and 232, wipers 231 and 292 and the selectors incoming conductors which are accessible to said wipers. The line relay and hold relay of the selector will operate and return ground over private conductor of the selector, wiper 296 and operated contacts 234 to hold R230 operated and also over contacts 233, conductor 178 and contacts 133 to hold R130 operated.

When R230 operated it opened contacts 238 to remove ground potential from the hold conductor 174. Ground over contacts 260 and 239, conductor 184, contacts 138, guard conductor 172 and contacts 341 energize the allotter motor magnet M310. If no other call is waiting and R120 restores to remove ground from start conductor 171, start relay R330 restores. R340 will restore in response to the restoration of R330; M310 will restore to advance the allotter one step, thereby to preselect the next accessible finder. If said next finder is busy, ground over its guard conductor and contacts 331, 321 and 311 will energize M310, and self-interrupting contacts 311 will restore M310 to advance the allotter wipers to the next finder. In this manner, allotter 300 will preselect an idle finder. If all finders are busy, normally operated relay R320 will restore to open contacts 321 thereby to prevent needless operation of the allotter.

If, when finder 102 and secondary switch 200 extended the line associated with substation 100, another call was waiting on a line associated with allotter' 300, ground will be maintained on conductor 171 after R120 restores by way of contacts-corresponding to 125--on the line relay associated with said last-mentioned line. R330 will still restore since its operating circuit will be opened at contacts 311 when M310 energizes, and M310 will restore when R340 restores to advance the allotter wipers as previously described. When an idle finder is found, it will be taken into use to extend said other call.

When relays R130 and R230 operate, they remove at contacts 130 and 240 multiple ground potentials from the all trunks busy conductor 173.

After the calling line has been extended to an idle selector by finder 102 and switch 200, connections to a called line are completed over a switch train in a manner well known in the art. Holding ground for the switching relays R130 and R230 is provided from the connector in the witch train. When the call is termid hated and the customer at substation replaces the handset on the receiver to open the calling line, the connector line and holdrelays restore to remove the holding ground from the private conductor. R and R230 will restore followed by the restoration of cutoif relay R110. When R230 restores contacts 241' and 242, ground over cit-normal contacts 298, contacts 261, 241 and 221 and self-interrupting contacts 271 will energize the upper winding of the motor magnet M270; and ground over contacts 290, 263, 242, 223 and 272 will energize the lower winding of M270. M270 will operate, open contacts 271 and 272, and restore to advance the wipers one step. M270 will be reoperated by means of said circuits until the wipers return to their normal position at which time ofi-normal contacts 298 and 299 open. During the return or" the secondary switch wipers to normal, said switch will be busy marked by ground over off-normal contacts 297 and 217 to the guard conductor 172.

While there has been described what is at present considered to be the preferred embodiment of the invention, various modifications may be made therein; and it is contemplated to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. For use in a telephone system having a plurality of pairs of lines and one potential condition connected to some of said lines and another potential condition connected to others of said lines, a switch with two sets of wipers having access to said pairs of lines, said switch comprising a magnet having two windings and a single armature, each of said windings corresponding to one of said wiper sets; a switching relay corresponding to each wiper set; means for connecting said windings and said relays to the wiper sets corresponding thereto; circuit means operated and effective in response to a wiper set encountering said one condition for operating the switching relay connected thereto, and operated and effective in response to a wiper set encountering said other condition for energizing the winding connected thereto and for preventing an operation of the switching relay connected thereto; armature-controlled means operated and efiective only in response to an energization of both windings for advancing the wipers one step; and contacts operated in response to the operation of a switching relay for switching through connections to its respective wiper set, said wipers thereby being advanced over pairs of lines to a line having said one condition connected thereto a connection thereby being switched through to the wiper set encountering said last-mentioned line.

2. In a switch as claimed in claim 1, means operated responsive to both of said Wiper sets encountering said one condition on a pair of lines for preventing the operation of one of said switching relays, thereby to prevent switching through connections to both of said Wiper sets.

3. In an automatic switch having two sets of wipers and pairs of lines accessible to said wiper sets, a particular potential condition normally connected to each of said lines; a magnet having two windings and a single armature; means for energizing each of said windings; means whereby said last means is operated to energize one of said windings when one set of wipers encounters said condition on one of said lines and to energize the other winding when the other set of wipers encounters said condition on the line paired with said one line; means including said armature for advancing said wipers over said pair of lines; and means associated with said magnet whereby said last means is operated only in response to the energization of both windings.

4. In a switch as claimed in claim 3, a pair of switching relays, means for connecting each of said relays to a respective one of said wiper sets, means for operating each of said relays, and means whereby said last means is operated to operate one of said relays if the wiper set connected thereto encounters a condition other than said particular potential condition. I 5. In a switch as claimed in claim 4, means operated and effective for preventing the operation of one of said relays when both wiper sets encounter conditions other than'said particular condition on a pair of lines.

6. In a telephone system having a plurality of pairs calling line; a finder switch with two sets of wipers having access to said pairs of lines, said finder comprising a magnet with two windings and a single armature, each of said windingsv corresponding to one set of said wipers; a switching relay corresponding to each set of said wipers; means for connecting said windings tion of both windings for advancing the wipers one step, the wipers thereby being advanced when the wipers encounter a pair of idle lines and being stopped when one set of wipers encounters the calling line; and contacts operated in response to the operation of the switching relay connected to said one set of wipers for switching through connections to said calling line.

7. In a combination as claimed in claim 6, said finder also comprising means operated in response to said wipers encountering a pairof calling lines for preventing the operation of one of said switching relays, whereby connections are switched through to only one of said pair of calling lines.

8. For use in a telephone system having a plurality of pairs of lines and having one potential condition connected to some of said lines, a switch with two test wipers, for simultaneously testing pairs of lines for said conditions, said switch comprising a magnet with two windings and a single armature; a switching relay connected to each of said windings; circuits including the winding of each one of said relays and the magnet Winding connected thereto for operating each relay; means for completing both of said circuits and for connecting each of said test wipers to one of said cir-.

cuits atthe connection between the relayv and magnet winding therein; said one potential encountered by a test wiper energizing the magnet winding connected thereto and preventing an operation of the relay connected thereto; armature-controlled means operated only in response to the energization of both magnet windings for advancing the wipers one step to the next pair of lines, said wipers thereby advancing each time both of of lines and a potential condition normallyconnected to each of said lines, a calling one of said lines; means for changing the potential condition associated with said said test wipers encounter said one potential condition on a pair of lines and stopping when one of saidytest wipers encounters a condition other than said one po.

tential condition at which time the switching relay connected to said last mentioned test wiper operates over its operating circuit.

9 Ina switch as claimed in claim 8, means operated in response to .both of said test wipers encountering a condition other than said one potential conditon for preventing the operation of one of said switching relays.

10. In a telephone system having a plurality of pairs of subscriber lines over which calls are made, a finder switch having two sets of wipers having access to .said pairs of lines; a secondary switch, connected to said finder switch, having two sets of Wipers; a plurality of pairs of trunks accessible to saidsecondary wipers; each of said switches including a motor magnet having two windings and a single armature and each including two switching I relays; meansfor connecting each wiper set to a corresponding relay and Winding; circuit means operated and effective in response to the initiation of a call for energizing each winding of the finder magnet whenever the finder wiper set connected thereto encounters a non-calling wipers advancing only when a'pair of busy trunks are 1 encountered; circuit means operated and effective in response to one of said finder wiper sets encountering said calling line for operating the finder switching relay connected thereto; circuit means operated and efiective in response to one of said secondary wiper sets encountering an idle one of said trunks for operating the secondary switching relay connected thereto; and contacts on said 1 operated finder and secondary switching relays operated for connecting said calling line to said one idle trunk by way of the wiper sets connected thereto.

11. In a combination as claimed in claim 10, means responsive to said finder vwiper sets encounteringa pair of calling lines for operating only one of said finder switching relays and means responsive to said secondary wiper sets encountering a pair of idle trunks for operating only one of said secondary switching relays.

References Cited in the file of this patent UNITED STATES PATENTS 1,521,160 McPherson t Dec. 30, 1924 1,641,788 Thomas et a1 Sept. 6, 1927 2,214,908 Lornax et al. Sept. 17, 1940 OTHER REFERENCES I Telephony---Atkinson, pages 56, and 66, 1948.

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